This application claims the priority of Korean Patent Application No. 2003-72500, filed on Oct. 17, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a light tunnel for providing a uniform light which has an improved structure enabling a compact optical arrangement, a uniform light illuminating device using the light tunnel, and a projector which employs the light tunnel and the uniform light illuminating device.
2. Description of the Related Art
In general, projectors provide an image onto a screen by using an illuminating device and an image display device. Image display devices include digital micro-mirror devices (DMDs), transmission type LCDs and reflection type liquid crystal on silicon (LCOSs). A uniform light illuminating device makes light emitted from a lamp have a uniform profile and is widely used in projection optical devices such as projectors.
Referring to FIG. 1, a conventional uniform light illuminating device includes a light source 10 emitting light, a light tunnel 13 converting the light emitted from the light source 10 to a uniform light and a relay lens unit 15.
The light source 10 includes a lamp 11 for generating light, and a reflection mirror 12 for reflecting part of the light emitted from the lamp 11 along a predetermined light path. The lamp 11 generates light utilizing arc discharge. Thus, the light emitted from the light source 10 is not uniform because the light is affected by the arc gap and by the portion of the light emitted from the lamp 11 which is not reflected by the reflection mirror 12.
The light tunnel 13 can be a glass rod having a cube shape which changes the light emitted from the light source 10 to a uniform light. That is, light incident on an incident surface 13a of the light tunnel 13 at a predetermined inclination angle is totally reflected by a side wall 13b and proceeds toward an exit surface 13c. Accordingly, by scrambling the incident light using a total reflection principle, a uniform light is produced from the light tunnel 13.
In the light tunnel 13, the incident surface 13a and the exit surface 13c are arranged to direct the ultimately reflected light rays in opposite directions from the incoming light rays. In the conventional uniform light illuminating device, the light source 10 is disposed to face the incident surface 13a and the relay lens unit 15 is disposed to face the exit surface 13c. Thus, the width D1 of the uniform light illuminating device is determined by the overall arrangement of the light source 10, the light tunnel 13 and the relay lens unit 15 such that a large space is needed to accommodate these components. However, when the uniform light illuminating device is used in a projector, the components must fit in a limited amount of space.